1. Technical Field of the Invention
The present invention relates to clock distribution and alarm collection schemes in telecommunications equipment and, more particularly, to a bus control module provided as a terminating stage in a multi-stage clock distribution and alarm collection system in a network platform (e.g., a Next Generation Signaling Transfer Point (STP)) for use in Signaling System No. 7 (SS7) networks.
2. Description of Related Art
Out-of-band signaling establishes a separate channel for the exchange of signaling information between call component nodes in order to set up, maintain and service a call in a telephony network. Such channels, called signaling links, are used to carry all the necessary signaling messages between the nodes. Thus, for example, when a call is placed, the dialed digits, trunk selected, and other pertinent information are sent between network switches using their signaling links, rather than the trunks which will ultimately carry the bearer traffic, i.e., conversation.
Out-of-band signaling has several advantages that make it more desirable than traditional in-band signaling. First, it allows for the transport of more data at higher speeds than multi-frequency (MF) outpulsing used in the telephony networks of yore. Also, because of separate trunks and links, signaling can be done at any time in the entire duration of the call, not just at the beginning. Furthermore, out-of-band signaling enables signaling to network elements to which there is no direct trunk connection.
SS7 packet signaling has become the out-of-band signaling scheme of choice between telephony networks and between network elements worldwide. Three essential components are defined in a signaling network based on SS7 architecture. Signal Switching Points (SSPs) are basically telephone switches equipped with SS7-capable software that terminate signaling links. They generally originate, terminate, or switch calls. Signal Transfer Points (STPs) are the packet switches of the SS7 network. In addition to certain specialized functions, they receive and route incoming signaling messages towards their proper destination. Finally, Signal Control Points (SCPs) are databases that provide information necessary for advanced call-processing and Service Logic execution.
As is well known, SS7 signaling architecture is governed by several multi-layered protocols standardized under the American National Standards Institute (ANSI) and the International Telecommunications Union (ITU) to operate as the common “glue” that binds the ubiquitous autonomous networks together so as to provide a “one network” feel that telephone subscribers have come to expect.
The exponential increase in the number of local telephone lines, mobile subscribers, pages, fax machines, and other data devices, e.g., computers, Information Appliances, etc., coupled with deregulation that is occurring worldwide today is driving demand for small form factor, high capacity STPs which must be easy to maintain, provide full SS7 functionality with so-called “five nines” operational availability (i.e., 99.999% uptime), and provide the capability to support future functionality or features as the need arises. Further, as the subscriber demand for more service options proliferates, an evolution is taking place to integrate Intelligent Network (IN)-capable SCP functionality within STP nodes.
While it is generally expected that a single platform that supports large-database, high-transaction IN services as well as high-capacity packet switching (hereinafter referred to as a signaling server platform) will reduce equipment costs, reduce network facility costs and other associated costs while increasing economic efficiency, those skilled in the art should readily recognize that several difficulties must be overcome in order to integrate the requisite functionalities into a suitable network element that satisfies the stringent performance criteria required of telecommunications equipment. Daunting challenges arise in designing a compact enough form factor that is efficiently scalable, ruggedized, and modularized for easy maintenance, yet must house an extraordinary constellation of complex electronic circuitry, e.g., processors, control components, timing modules, I/O, line interface cards which couple to telephony networks, etc., that is typically required for achieving the necessary network element functionality. Whereas the electronic components may themselves be miniaturized and modularized into cards or boards, interconnecting a large number of such cards via suitable bus systems and controlling such interconnected systems poses many obstacles.
Conventional bus masters (which manage a bus segment and the devices or cards disposed thereon) and bus master arrangements are beset with numerous deficiencies and drawbacks in this regard. In the existing arrangements, for example, the bus master occupies one of the fixed number of slots (i.e., system board slot) provided with the bus segment, thereby reducing the number of slots available for other cards, i.e., peripherals. Where peripheral connectivity is at a premium, such as a network element requiring a large number of line interface cards in a compact form factor, such a situation is undesirable.
Also, current bus master cards are typically based on a processing element for their functionality. Although processor-based bus masters possess “higher intelligence,” such cards have less overall reliability because processors, as a class of electronic devices, have higher Failures per Billion Operating Hours (FITs) in general. Again, in stringent telecommunications environments, this reduced overall reliability poses an unacceptable risk of failure.
Furthermore, when processor-based bus masters are used in current arrangements, processors similar to bus master processors cannot be used for peripherals that are designed to contain processors. Two different types of hardware need to be maintained accordingly, which can also give rise to a reliability risk in addition to increased maintenance costs.
Where the use of non-standard system boards is desired in order to overcome the aforementioned deficiencies, typically in telecommunications equipment, such boards must be capable of operating effectively within the equipment's clock distribution scheme provided for distributing internal clock signals (i.e., telecommunication clocks) to the line interface cards. This is particularly applicable in systems required to provide tightly controlled telecommunication clocks in a reliable manner in highly scalable architectures which also include redundancy.
In addition, as those skilled in the art should readily appreciate, current techniques for collecting alarm and status data from a huge number of sources (typically the cards themselves) in telecommunications equipment are inadequate because they require running separate cables from each alarm source to a centralized controller of the system. Clearly, with thousands of cards that may be needed for achieving the necessary network element functionality, such an arrangement creates an unmanageable cabling problem with attendant potential reliability hazards. Moreover, such concerns are heightened when small form factor requirements are imposed.